1. Field of the Invention
The invention relates to a pressure valve for a compressor.
2. Description of the Prior Art
Pressure valves of this kind are disposed on the pressure side of compressors. In known pressure valves according to the state of the art, a valve spring, a damper element which is not absolutely necessary, and a holding-down element are arranged above a pressure bore of a valve plate, with one element being situated above the other. All elements are located in a volume enclosed by the valve plate and the cylinder cover, with both being fastened to the cylinder by means of screws. During the compression cycle of the compressor the valve spring opens through the pressure of the medium in the pressure bore and the spring flips upwardly. It is not necessarily braked by a damper element. The stroke of the valve spring is also not necessarily limited by a holding-down element. Once the compression cycle has been completed, the spring flips over the pressure bore again as a result of the spring power and the difference in pressure, and closes the same.
U.S. Pat. No. 5,110,272 discloses a pressure valve which comprises a valve spring, a damper element and a holding-down element comprising a pin. The serious disadvantage as compared with the pressure valve in accordance with the invention is the fact that a recess is provided in the valve plate which renders machining more difficult and that it is additionally necessary that the holding-down element must be fastened to the valve plate by means of rivets. As compared with the pressure valve in accordance with the invention this means a substantially longer production time and substantially more material that needs to be processed when considering piece numbers of several million per year.
DE 33 05 791 A1 also discloses a pressure valve for a compressor in which the valve plate comprises an oblong recess into which an insert is placed on which pins are arranged. Said pins stand normal to the plane of the valve plate and the insert. The valve spring, the damper element and the holding-down elements are provided with recesses which can be brought into engagement with said pins. As a result, these elements are fixed in their position.
The disadvantage of this type of pressure valve is the labour-intensive production. It is first necessary to mill an oblong recess into the valve plate, whereby it is necessary to ensure that the surface roughness on the valve seat does not exceed the stated tolerances. Subsequently, it is necessary to produce an insert which is inserted into the previously milled oblong recess. The volume of material that is removed first by metal cutting is then partly refilled again. The entire pressure valve further comprises an insert, a valve spring, an additional leaf spring, a catching plate as well as a bridge spring, thus five parts which entail a considerable amount of assembly work.
Pressure valves are further known whose valve plate is not provided with any recess, but where the valve spring, the damper element and the holding-down element(s) are fastened to the valve plate by means of rivets. Such a design also means additional manufacturing work, since at least one riveting machine needs to be used. Moreover, the disassembly of this arrangement for repair purposes is rendered more difficult, if not even impossible, due to the rivets. A pre-assembly of the valve plate including the valve spring, damper element and holding-down element is not possible, since they concern loosely inserted parts which does not allow any simple handling of the unit thus produced.
DE-AS 1 503 406 discloses a valve arrangement in which a stop plate and a tensioning leaf spring are arranged above a pressure-valve leaf spring. These elements are in engagement with two pins which are inserted in bores in the valve plate and the cylinder cover and thus ensure the unity of the arrangement. There are two specific disadvantages as compared with the present invention. The complex fastening of the pressure-valve leaf spring by means of the four parts instead of one part as in the present invention leads to a considerably higher amount of manufacturing work and increases the probability of the failure of the entire pressure valve. The opening valve spring is not subjected to any damping, whereas the possibility of the provision of a damper element was considered in the present application. Moreover, the pressure valve disclosed in the cited specification concerns the principle of intake compression which differs from the present application. DE-AS 1 503 406 discloses two separate suction sound boxes as well as a central pressure bore. This leads to a higher suction gas preheating, which on the other hand leads to higher work to be done on the compression.